1. Field of the Invention
The present invention relates to a monolithic ceramic electronic component, and particularly to, for example, a monolithic ceramic electronic component in which outer electrodes are provided on both end surfaces of a multilayer body.
2. Description of the Related Art
In recent years, a large number of electronic components such as ceramic electronic components have come to be mounted on circuit substrates installed in electronic equipment. For mounting such electronic components on circuit substrates, Pb-containing solder has been commonly used. However, in recent years, in order to reduce environmental loads, studies on Pb-free mounting of electronic components have been increasingly performed.
In a known example of a Pb-free method of mounting electronic components on circuit substrates, electronic components are mounted with Pb-free solder or a conductive adhesive containing a thermosetting resin such as an epoxy thermosetting resin and conductive fine particles such as metal filler. A monolithic ceramic electronic component that is suitable for such mounting includes a ceramic body having inner electrodes formed of Ni or Ni alloy, and has, on the end surfaces of the ceramic body, outer electrodes each constituted by a lower electrode mainly formed of Cu or Cu alloy and an overlying outermost electrode layer mainly formed of Ag or Ag alloy. In such an electronic component, by forming Ag-containing electrode layers as outermost electrode layers of outer electrodes, the outer electrodes have enhanced compatibility with conductive adhesive to thereby increase the mounting strength of the electronic component (refer to Japanese Unexamined Patent Application Publication No. 2002-158137, for example).
However, in the monolithic ceramic electronic component described in Japanese Unexamined Patent Application Publication No. 2002-158137, electrochemical migration of Ag may cause short circuit failures between outer electrodes. In particular, for example, in the cases where electronic components are used within or near ECUs (electric control units) of automobiles, the atmosphere around electronic components may have a high temperature of 150° C. or more. In such an atmosphere, short circuit failures easily occur in the monolithic ceramic electronic component described in Japanese Unexamined Patent Application Publication No. 2002-158137 due to electrochemical migration of Ag.
As illustrated in FIG. 6, a conductive adhesive 3 is applied to lands 2 of a circuit substrate 1 and a monolithic ceramic electronic component 4 is mounted on the conductive adhesive 3. At this time, the monolithic ceramic electronic component 4 presses down on the conductive adhesive 3. This may cause the conductive adhesive 3 to spread to the surface of a ceramic body 5 or to the space between the ceramic body 5 and the circuit substrate 1; or a capillary phenomenon may cause the conductive adhesive 3 to move along the surface of the ceramic body 5. As a result, the conductive adhesive 3 may form a connection between outer electrodes 6, causing short circuit failures.